Mauricio Benitez, left, and Bret Wassink, both of Port Angeles, ride their bicycles on a section of the Waterfront Trail at the fenced-off edge of the former Rayonier mill site in Port Angeles. -- Photo by Keith Thorpe/Peninsula Daily News

PORT ANGELES — A portion of Waterfront Trail will close beginning today when crews begin digging a 15-foot-wide trench for the city’s $41.7 million combined sewer overflow project and depositing the dirt in giant bins on the defunct Rayonier Inc. pulp mill site.

Construction work will close a portion of the trail stretching from the Olympic Medical Center to the trail’s intersection with North Ennis Street until Nov. 30, city project manger James Burke said last week.

Starting Monday, pedestrians will be detoured starting at Francis Street east along Georgiana Street and back to the trail north along Ennis Street.

Crews from Ferndale-based IMCO General Construction will complete the work as part of Phase I of the city’s larger combined sewer overflow — or CSO — project, which will eventually extend sewer lines along the Waterfront Trail from downtown Port Angeles through the former Rayonier mill site to the city’s wastewater treatment plant.

The trench, which will be from 6-feet to 8-feet deep, will hold three pipes for the project.

It will run parallel to Waterfront Trail and from the west end of the Rayonier site east to the west end of a soon-to-be-built 105-foot bridge over Ennis Creek, Burke said.

Sixteen piles have been installed for the new bridge and dirt excavated for the bridge abutments, city Public Works & Utilities Engineering Manager Kathryn Neal said Friday.

The span will carry the new sewer lines over Ennis Creek and eventually become part of the Waterfront Trail.

Crews will fill in the trench with clean dirt, Burke said.

The excavated dirt will be stockpiled on the Rayonier mill site in eight bins, each with a capacity of about 2,000 cubic yards, or about 200 dump-truck loads, Rayonier cleanup project manager Warren Snyder said Friday.

The estimated volume of excavation of all the trenching that will be done on the Rayonier property is 16,100 cubic yards, Neal said, enough to fill all eight bins.

The material will be sample-tested for pollutants already determined to be present at the site, “metals, PCBs, things like that,” Snyder said.

The 75-acre property, the largest undeveloped waterfront parcel on the North Olympic Peninsula, became a state Department of Ecology cleanup site in 2000 due to concentrations of petroleum, metals, polychlorinated biphenyls, dioxins and pesticides left behind after Rayonier’s mill closed and was torn down in 1997, after 68 years of production.

Earlier this year, an agreement pushed the date for a cleanup plan to December 2014.

The additional sewer lines are designed to prevent untreated wastewater and storm water from flowing into the harbor during heavy storms.

Ecology is giving the city until 2016 to complete the project or face fines of up to $10,000 per day during sewage overflows.

The piping “is kind of the heart of the [CSO] project,” Neal said, adding that workers are also restoring a 5-million-gallon tank that the city purchased from Rayonier to store excess storm water runoff and sewage.

The city purchased the tank and 12 acres of Rayonier property for $995,000.

Burke estimated crews could finish the trenching and pipe installation before Nov. 30 but are taking their time in case unexpected harmful substances or archaeological remains are found.

Neal said archaeological investigations last summer don’t suggest significant material will be found, though archaeologists and representatives from the Lower Elwha Klallam Tribe will be monitoring construction since the area was once the site of an ancient Klallam village.

“[Archaeological concerns] have been a factor in this project since the beginning,” Neal said.

Snyder said about 90 percent of contaminated soil has been removed from the Rayonier site and that the company is waiting for the state Department of Ecology to complete a study of pollution in Port Angeles Harbor.

“What we are talking about now is the final phase of cleanup of the property,” Snyder said Friday.

Rayonier spokesman Charles Hood estimated last week that the company has spent “north of $35 million” since cleanup began in 2000.

“I would imagine that when this process started, we would have concluded it by now,” Hood said.

“With that backdrop, I’m not sure we have a final time line that we are very confident of.”